What this means is that there are two ways for you to

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Unformatted text preview: the desired sentence and then clicking OK. At other points in the game, you will be asked to pick a block satisfying some formula. You do this by moving the cursor over the desired block and selecting it. Then click OK. If necessary, Tarski’s World assigns a name to the chosen block, for example n1, and labels it. 3.5.2 Backing up and giving up Tarski’s World never makes a mistake in playing the game. It will win if it is possible for it to win, that is, if your initial commitment was wrong. However, you may make a mistake, and so lose a game you could have won. All it takes is some bad choices along the way. Tarski’s World will take advantage of you. It will not tell you that you made a bad move until it has won, when it will inform you that you could have won. What this means is that there are two ways for you to lose: if you were wrong in your initial assessment, or if you make a faulty choice in the play of the game. To put this more positively, if you win a game against the computer, then you can be quite sure that your initial assessment of the sentence, as well as all subsequent choices, were correct. To make up for the edge the computer has, Tarski’s World allows you to retract any choices you have made, no matter how far into the game you’ve gone. So if you think your initial assessment was correct but that you’ve made a bad choice along the way, you can always retract some moves by clicking on the Back button. If your initial assessment really was correct, you should, by using this feature, eventually be able to win. If you can’t, your initial commitment was wrong. The Back button undoes the last step of the game, while the Reconsider button undoes all of the moves since the last time that you made a choice. If, halfway through the play of the game, you realize that your Using Tarski’s World / 27 assessment was wrong and understand why, you can stop the game by clicking the End Game button. This ends the game, but does not shut down Tarski’s World. 3.5.3 Controlling the interaction in the game There are three checkboxes which can be used to control the detail with which the game is presented. Some moves can be carried out completely automatically rather than require you to click a confirmation button. We recommend leaving these in the checked (most verbose) position until you gain some experience with the game. The function of these checkboxes are described below ◦ Rewrites: At some points in the game one formula is replaced by another equivalent formula. This is how implications and biconditionals are handled. Since there are no choices to be made at this point, you can make the game proceed with these replacements without requiring interaction by switching off this checkbox. ◦ Formula Choices: At some points in the game Tarski’s World must choose one formula from a range of choices. Since the are choice is out of your control, you can make the game proceed with these choices without requiring interaction by switching off this checkbox. Of course, when you are re...
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This document was uploaded on 01/26/2014.

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